THz EPR-on-a-Chip for Enhanced Spin Sensitivity

电子顺磁共振(EPR)是化学、物理、医学和材料科学中最强大的分析方法之一。它利用自由基电子自旋作为探针来解析复合材料和界面的结构-功能关系。不幸的是，由于传统使用的基于谐振器的测量原理，EPR的广泛应用潜力被非常高的仪器成本、中等的灵敏度以及样品环境中的灵活性不足所抵消。该项目旨在通过将最近推出的EPR-on-a-Chip(EPRoC)方法从GHz扩展到THz，从而克服EPR的上述局限性。EPRoC方法将整个自旋激发源和探测器集成到单个集成电路上。总体而言，该项目将产生的新的太赫兹EPRoC光谱仪将极大地降低太赫兹EPR的实验复杂性，同时提供前所未有的灵敏度和光谱分辨率，至少比GHz EPRoC高两个数量级。为此，我们将从理论上和实验上研究一类新型的压控振荡器(VCO)，它利用分离式电感作为太赫兹磁场源和EPR探测器。在该项目中，我们将应用这项新的THz技术来研究高效晶体硅单结和具有非晶硅选择接触层的串联钙钛矿型太阳能电池界面区域的缺陷。在这里，我们将通过检测太阳能电池电流中的顺磁缺陷作为磁性指纹，实现前所未有的仅数百个缺陷的灵敏度，无论是在环境运行条件下还是在液氦温度下。该项目将展示太赫兹电子顺磁共振光谱的巨大应用潜力，并将有助于为太赫兹电子顺磁共振光谱在材料科学、分析化学和生物医学研究中的广泛应用铺平技术道路。

Electron paramagnetic resonance (EPR) is amongst the most powerful analysis methods in chemistry, physics, medicine, and materials science. It utilizes radical electron spins as probes to resolve the structure-function relationship of complex materials and interfaces. Unfortunately, EPR’s broad application potential is offset by very high instrumentation costs, moderate sensitivity, and insufficient flexibility in the sample environment due to the conventionally used resonator-based measurement principle. The proposed project aims at overcoming the aforementioned limitations of EPR by extending the recently introduced EPR-on-a-chip (EPRoC) approach, which integrates the entire spin excitation source and detector onto a single integrated circuit, from the GHz into the THz regime. Overall, the new THz EPRoC spectrometer that will emerge from the project will greatly reduce the experimental complexity of THz EPR and, at the same time, provide unprecedented sensitivity and spectral resolution, being at least two orders of magnitude better than GHz EPRoC. To this end, we will both theoretically research and experimentally investigate a new class of voltage-controlled oscillators (VCOs) that make use of split inductors as THz magnetic field sources and EPR detectors. Within the project, we will apply this new THz technology to study defects located in the interface region of the high-efficiency crystalline silicon single junction and tandem perovskite solar cells with an amorphous silicon selective contact layer. Here, we will achieve an unprecedented sensitivity of only a few hundred defects by detecting the paramagnetic defects as a magnetic fingerprint in the solar cell’s current, both under ambient operating conditions and at liquid helium temperatures. The project will demonstrate the immense application potential of THz EPRoC spectroscopy and will help to pave the technological road for a broad application of THz EPR spectroscopy in materials science, analytical chemistry, and biomedical research.